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SubjectRe: bloat-o-meter +32832 (was: Re: bpf: add prog_digest and expose it via fdinfo/netlink)
On 12/13/2016 10:29 AM, Geert Uytterhoeven wrote:
> Hi Daniel,
>
> On Mon, Dec 12, 2016 at 6:08 PM, Linux Kernel Mailing List
> <linux-kernel@vger.kernel.org> wrote:
>> Web: https://git.kernel.org/torvalds/c/7bd509e311f408f7a5132fcdde2069af65fa05ae
>> Commit: 7bd509e311f408f7a5132fcdde2069af65fa05ae
>> Parent: 8d829bdb97dc3a0c9c8090b9b168ca46ea99c8d8
>> Refname: refs/heads/master
>> Author: Daniel Borkmann <daniel@iogearbox.net>
>> AuthorDate: Sun Dec 4 23:19:41 2016 +0100
>> Committer: David S. Miller <davem@davemloft.net>
>> CommitDate: Mon Dec 5 15:33:11 2016 -0500
>>
>> bpf: add prog_digest and expose it via fdinfo/netlink
>>
>> When loading a BPF program via bpf(2), calculate the digest over
>> the program's instruction stream and store it in struct bpf_prog's
>> digest member. This is done at a point in time before any instructions
>> are rewritten by the verifier. Any unstable map file descriptor
>> number part of the imm field will be zeroed for the hash.
>>
>> fdinfo example output for progs:
>>
>> # cat /proc/1590/fdinfo/5
>> pos: 0
>> flags: 02000002
>> mnt_id: 11
>> prog_type: 1
>> prog_jited: 1
>> prog_digest: b27e8b06da22707513aa97363dfb11c7c3675d28
>> memlock: 4096
>>
>> When programs are pinned and retrieved by an ELF loader, the loader
>> can check the program's digest through fdinfo and compare it against
>> one that was generated over the ELF file's program section to see
>> if the program needs to be reloaded. Furthermore, this can also be
>> exposed through other means such as netlink in case of a tc cls/act
>> dump (or xdp in future), but also through tracepoints or other
>> facilities to identify the program. Other than that, the digest can
>> also serve as a base name for the work in progress kallsyms support
>> of programs. The digest doesn't depend/select the crypto layer, since
>> we need to keep dependencies to a minimum. iproute2 will get support
>> for this facility.
>>
>> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
>> Acked-by: Alexei Starovoitov <ast@kernel.org>
>> Signed-off-by: David S. Miller <davem@davemloft.net>
>
>> --- a/kernel/bpf/core.c
>> +++ b/kernel/bpf/core.c
>> @@ -136,6 +136,71 @@ void __bpf_prog_free(struct bpf_prog *fp)
>> vfree(fp);
>> }
>>
>> +#define SHA_BPF_RAW_SIZE \
>> + round_up(MAX_BPF_SIZE + sizeof(__be64) + 1, SHA_MESSAGE_BYTES)
>> +
>> +/* Called under verifier mutex. */
>> +void bpf_prog_calc_digest(struct bpf_prog *fp)
>> +{
>> + const u32 bits_offset = SHA_MESSAGE_BYTES - sizeof(__be64);
>> + static u32 ws[SHA_WORKSPACE_WORDS];
>> + static u8 raw[SHA_BPF_RAW_SIZE];
>
> function old new delta
> raw - 32832 +32832
>
> Congratulations!
> We've found the first nominee for the v4.10-rc1 bloat-o-meter contest! :-(
>
> Can this please be allocated dynamically? Thanks!

Sure, should be okay since mostly slow-path. Will send a patch.

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